Recently, due to an increase in emission of carbon dioxide according to consumption of fossil fuel, a sudden change in crude oil prices, and the like, technology development for converting gasoline and diesel as an energy source for a vehicle into electric energy has been receiving attention. An electric vehicle has been commercialized and thus there is a need to increase capacity and energy density of a battery, in detail, a lithium ion battery which is a battery for long distance driving of the electric vehicle. However, the current lithium ion battery has a limited battery capacity and therefore has a difficulty in long distance driving. Therefore, a lithium air battery having larger capacity and higher energy density than the lithium ion battery in theory has been receiving attention.
The lithium air battery has a battery having a cathode using oxygen in air as an active material and is a battery which may be charged and discharged in response to an oxidization and reduction reaction of oxygen in the cathode.
Generally, the lithium air battery includes an anode in which lithium ions may be adsorbed and emitted, a cathode including an oxidization and reduction catalyst of oxygen using oxygen in air as a cathode active material, and a lithium ion conductive medium disposed between the cathode and the anode.
Further, the lithium air battery has a theoretical energy density of 3,000 Wh/kg or more, which corresponds to energy density approximately 10 times larger than that of the lithium ion battery. Further, the lithium air battery may be eco-friendly and may have more improved stability than that of the lithium ion battery.
However, the lithium air battery has a problem in that an electrolyte solvent of an electrolyte part is evaporated. The electrolyte solvent is evaporated inside the lithium air battery. Therefore, ion conductivity of the electrolyte inside the lithium air battery is not only reduced but performance of the lithium air battery is also degraded, and an operation of the lithium air battery abruptly ends and thus the lithium air battery may be instable. Therefore, a lithium air battery system capable of ensuring the stability of the lithium air battery is required.